Various apparatus and procedures are well known in the art for determining surface tension. One such process is known as the maximum bubble pressure method. This process is described in Arthur W. Adamson's Physical Chemistry of Surfaces, 4th Edition, published by John Wiley and Sons, 1982, on page 18. This process requires a relatively large volume of fluid.
Apparatus known for determining surface tension includes the Wilhelmy balance which is available from the Kahn Company. Another apparatus is the Pulsating Bubble Surfactometer apparatus available from the Electronetics Corporation. The Wilhelmy balance apparatus will not tell whether or not a preparation of pulmonary surfactant has the ability to keep a narrow tube open. Furthermore, it is slow, requires a relatively large volume of fluid, and the cleaning procedures are laborious. The Pulsating Bubble Surfactometer apparatus has the disadvantage that it will not tell whether or not a preparation of pulmonary surfactant is able to keep a narrow tube open, and furthermore it requires a large volume of at least 25 microliters.